1. Field of the Invention
The present invention relates to animal litter absorbent compositions and to processes for making the litter compositions. More particularly, the present invention relates to an animal litter absorbent composition based on calcium sulfate that may be used for both indoor pets and outdoor farm animals.
2. The Prior Art
Animal litters are useful for absorbing animal urine and to encapsulate animal feces until the litter is either cleaned-up or otherwise disposed of. The most commonly used absorbent materials are clays that are safe and non-irritating to the animal and that absorb relatively large amounts of liquids. Animal urine forms ammonia which has an unpleasant odor. The clay materials only absorb and hold urine resulting in a source of odor requiring frequent replacement and disposal of the litter.
Efforts have been made to develop a litter capable of disposing of both solid wastes and liquid wastes. This led to the development of clumping litters in the form of finely ground particles of certain clays, sometimes augmented by binders or additives to form discernable clumps when contacted by animal waste. These particles clump in the presence of liquid wastes, which is scooped up and removed with the solid wastes. Although the clumping litters enable a cat owner to remove waste without disposing of the entire contents of the litter box, these clumping litters are frequently dusty and the odor problem remains. Animal litters sometimes contain other absorbents such as wood chips, sawdust or sand but most of the cat litter products currently in commerce are manufactured from ground clay. These products are not water-soluble and thus are difficult to dispose of properly.
In addition to cat litter, problems exist with the growing environmental demand to ban waste water lagoons in mass production hog farms. The existing flush water systems currently in use by the swine industry are inadequate to control odor and pose other environmental risks by dangerous proximity to water tables.
A material useful as cat litter is described in U.S. Pat. No. 4,459,368 to Jaffe et al., which discloses a mixture of fuller's earth, preferably in the form of calcium bentonite, mixed with calcium sulfate dihydrate at a weight ratio of 1:9 to about 3:7. In addition, the particle size of the clay and the calcium sulfate dihydrate are such that no more than about 60 weight % of clay and about 20 weight % of calcium sulfate particle are retained on a 6 mesh sieve screen. The manner of mixing is not important as the clay and calcium sulfate dihydrate are simply mixed to form the cat litter. The patent states that the ratio of the weight of clay particles to the weight of calcium sulfate is important in order to maximize the liquid absorbing effect.
Another cat litter product is described in U.S. Pat. No. 5,469,809 to Coleman, wherein there is disclosed a litter having clumping characteristics. The litter comprises a mixture of opal clay and sodium bentonite formed into smooth round balls to eliminate dusting. There is also disclosed a cat litter having up to ten percent of a lignosulfonate. The lignosulfonate is said to help form and maintain a smooth round shape for the resulting litter granules. The litter is formed by mixing the opal clay and sodium bentonite, pelletizing in a disc pelletizer to form the spherical pellets and then screening to the desired size.
An animal litter that is said to form clumps is disclosed in the Elazier-Davis et al. patent, U.S. Pat. No. 5,452,684, directed to a method of agglomerating a smectite clay litter. Therein the clay is sheared in an extruder to align the clay platelets to produce a litter having stronger clumps. The smectite clay may be mixed with a small amount of water-soluble adhesive such as carboxymethylcellulose, alginate, starches, gums and the like to form the coherent clumps. The preferred clay is sodium bentonite which absorbs liquids such as urine and interacts with nearby clay particles to form strong clumps through physical reaction. However, this product simply holds the urine and does not reduce or eliminate the odor.
In addition to the above-disclosed litter products, it is also known that calcium sulfate may be mixed with soluble salts including urea to form a granulated soil additive product such as disclosed in U.S. Pat. No. 3,660,068 to Wilson. Along these same lines, U.S. Pat. No. 3,976,467 and 2,154,541, both to fertilizer-type products, also combine calcium sulfate or gypsum with urea.
Thus, there continues to be a need for an animal litter which is easily disposable. In addition there is need for an animal litter which has a high density to prevent tracking and in which the pungent ammonia odor of the animal urine is reduced.